Molecular Characterization of Trypanosoma cruzi in Infected Meccus pallidipennis in the Southern Region of the State of Mexico, Mexico

Trypanosoma cruzi in Wild and Synanthropic Mammals in Two Regions of Mexico: A Fieldwork and Genetic Discrete Typing Unit Review

Background: Marsupials and rodents are the most important wild and synanthropic hosts of Trypanosoma cruzi due to the high frequency of infection, maintenance of diverse genetic populations of the parasite, and their close proximity to interact with both transmission cycles, sylvatic and peridomestic. Our aim was to identify the discrete typing units (DTU) of T. cruzi from different wild and synanthropic hosts in two regions of Mexico and to carry out a review of historical data focusing on current knowledge on the diversity and T. cruzi DTUs of host species. Materials and Methods: One hundred fifteen samples were obtained from two areas in Tabasco and Nayarit state. The presence of T. cruzi was evaluated by PCR. Results: The 12.6% (12/95) of samples from Tabasco and 65% (13/20) from Nayarit were found to be positive for parasite DNA. All the sequences analyzed were grouped in T. cruzi DTU I; low nucleotide diversity was observed in Tabasco (π = 0.00566, and ϴ = 0.00632), while high genetic diversity was observed in Nayarit sequences, up to 8.63 (π) to 11.10 (ϴ) times greater than Tabasco sequences. Genetic flow and migration between Tabasco, and Nayarit were scarce (FST = 0.37329 and Nm = 0.42), and genetic exchange was observed only between nearby areas. The bibliographic review of hosts in Mexico, together with our data, shows a heterogeneous T. cruzi prevalence in Chiroptera and domestic animals. For Atelidae and Canids, prevalence is generally below 25%. However, a high prevalence, greater than 25% and up to 100%, was recorded in Didelphimorphia, and Rodentia. Few studies in regions of Mexico have been described as infected with the parasite; in these, the genetic group with the highest prevalence is the DTU I. Conclusion: Marsupials and rodents are important reservoirs of T. cruzi; DTU I was frequently reported; however, recent genetic and reservoir studies have demonstrated the presence of greater diversity of genetic groups.

Synanthropic triatomines in Hidalgo state, Mexico: Spatial-temporal distribution, domestic transmission cycle, and natural infection with Trypanosoma cruzi

Triatomine vectors are responsible for the main route of transmission of the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. This illness is potentially life-threatening and highly disabling and represents a major public health concern in the endemic countries in Latin America. The analysis of the spatial and temporal occurrence of triatomine insects is critical, since control strategies strongly depend on the vector species found within each area. Such knowledge is non-existent in Hidalgo state, an endemic region of Chagas disease in Mexico. A Geographic Information System (GIS) was used to analyze broad-scale spatial and temporal patterns of synanthropic triatomines collected in Hidalgo. Data was taken from the Institute of Epidemiological Diagnosis and Reference (InDRE) of Mexico and the state program of Vector Control of the Secretary of Health, covering the period of 1997-2019. Our analyses demonstrate a differential distribution of Triatoma dimidiata, T. mexicana, T. gerstaeckeri and T. barberi, which are the four predominant species, and that climate, temperature, and precipitation are some of the drivers of their distribution pattern. Notably, we report the presence of T. nitida, T. pallidipennis and T. phyllosoma for the first time in the state. In addition, we found seasonal variations of the populations of T. mexicana and T. gerstaeckeri, but not for T. dimidiata, whose population remains constant throughout the year. The insects were found mainly intradomicile (81.79 %), followed by peridomicile (17.56 %) and non-domestic areas (0.65%), with an average T. cruzi infection of 16.4%. Based on this evidence, priority sites for vector control intervention were identified. Our findings are very valuable for understanding the epidemiology of Chagas disease, the generation of future potential risk maps and for the development and implementation of effective and targeted vector control programs in Hidalgo state.

Trends in taxonomy of Triatomini (Hemiptera, Reduviidae, Triatominae): reproductive compatibility reinforces the synonymization of Meccus Stål, 1859 with Triatoma Laporte, 1832

BACKGROUND

Meccus' taxonomy has been quite complex since the first species of this genus was described by Burmeister in 1835 as Conorhinus phyllosoma. In 1859 the species was transferred to the genus Meccus and in 1930 to Triatoma. However, in the twentieth century, the Meccus genus was revalidated (alteration corroborated by molecular studies) and, in the twenty-first century, through a comprehensive study including more sophisticated phylogenetic reconstruction methods, Meccus was again synonymous with Triatoma. Events of natural hybridization with production of fertile offspring have already been reported among sympatric species of the T. phyllosoma subcomplex, and experimental crosses demonstrated reproductive viability among practically all species of the T. phyllosoma subcomplex that were considered as belonging to the genus Meccus, as well as between these species and species of Triatoma. Based on the above, we carried out experimental crosses between T. longipennis (considered M. longipennis in some literature) and T. mopan (always considered as belonging to Triatoma) to evaluate the reproductive compatibility between species of the T. phyllosoma complex. In addition, we have grouped our results with information from the literature regarding crosses between species that were grouped in the genus Meccus with Triatoma, in order to discuss the importance of experimental crosses to confirm the generic reorganization of species.

RESULTS

The crosses between T. mopan female and T. longipennis male resulted in viable offspring. The hatching of hybrids, even if only in one direction and/or at low frequency, demonstrates reproductive compatibility and homeology between the genomes of the parents.

CONCLUSION

Considering that intergeneric crosses usually do not result in viable offspring in Triatominae, the reproductive compatibility observed between the T. phyllosoma subcomplex species considered in the Meccus genus with species of the Triatoma genus shows that there is "intergeneric" genomic compatibility, which corroborates the generic reorganization of Meccus in Triatoma.

Susceptibility dynamics between five Trypanosoma cruzi strains and three triatomine (Hemiptera: Reduviidae) species

American trypanosomiasis is a zoonosis caused by the parasite Trypanosoma cruzi and is transmitted mainly by blood-sucking insects belonging to the subfamily Triatominae. The importance of this parasite lies in its wide geographical distribution, high morbidity, and the fact that there has not yet been an effective treatment or vaccine. Previous studies have detailed the interactions between different triatomine species and T. cruzi strains. However, the factors necessary to establish infection in triatomines have not yet been fully elucidated. Furthermore, it is postulated that the coexistence between the parasite and triatomines could modulate the susceptibility to infection in these insects. Accordingly, in this study, we evaluated the susceptibility to T. cruzi infection in the species Triatoma (Meccus) pallidipennis, Triatoma barberi, and Triatoma lecticularia, which were infected with Ninoa, H8, INC-5, Sontecomapan, and Hueypoxtla strains. The criteria used to establish susceptibility were the amount of blood ingested by the insects, percentage of infected triatomines, concentration of parasites in feces, and percentage of metacyclic trypomastigotes in feces. These parameters were analyzed by fresh examination and differential count with Giemsa-stained smears. Our main findings suggest the following order of susceptibility concerning infection with T. cruzi: T. lecticularia > T. barberi > T. (Meccus) pallidipennis. Furthermore, the study concludes that an increased susceptibility to infection of triatomines that share the same geographic region with different strains of T. cruzi is not always a fact.

An improved and low-cost protocol for high-quality DNA isolation for the Chagas disease vectors

An improved protocol for DNA extraction for the Chagas disease vectors is proposed based on modification to a low cost method described twenty years ago. Quality DNA and high molecular weight were obtained from all samples. NADH-4 gene was successfully amplified by PCR using the isolated DNA. The extraction protocol presented in this technical note is a fast, low-cost, and non-aggressive method to human health for obtaining genetic data from this group of epidemiological importance and potentially other insects.